Grease-like lubricants from animal fats and the alkaline components of fire-place ash is believed to be the earliest form of man's lubrication for his wooden wheel-and-shaft vehicles. First records noted use in Egypt of such materials blended with lime to lubricate chariots. After thousands of years, as the 19th century came to a close, fat- and vegetable-based greases were replaced with more easily manufactured and durable mineral oil based greases. Yet, bio-based greases derived from plant oil feedstock tend to have excellent tribological properties and generally have very high viscosities and flash points. They have some inherent disadvantages, however, such as sensitivity to hydrolysis and oxidation. See, Panchal, T., et al., “Bio-based Grease, a Value Added Product from Renewable Resources,” Ind. Crops Prod., 2015, 63, 48-52.
Today's revival of bio-based greases is being driven by an increased global focus towards the use of ecologically-friendly, environmentally safe materials. It is estimated that some 50% of all lubricants worldwide end up in the environment because of total loss applications, volatility, spills or accidents. See, Schneider, M., “Plant-oil Based Lubricants and Hydraulic Fluids,” J Sci. Food Agric., 2006, 86: 1769-1780. The introduction of legislation and consumer-driven initiatives such as the U.S. Environmental Protection Agency's Vessel General Permit, the European Union's Ecolabel scheme, and the U.S. Department of Agriculture's BioPreferred program has increased renewable and bio-sourced grease use. Such recent trends have primarily focused the grease industry on price and performance as well as biodegradability and ecological toxicity. See, Kimura, H., et al., “Properties and Applications of Synthetic Greases,” J. Synth. Lubr., 2003, 20, 241-255; Fish, G., “The Development of More Environmentally Considerate Greases,” 82nd NLGI Annual Meeting, Coeur d′Alene, Id., U.S.A., Jun. 6, 2015; Kumar, A., et al., “Challenges in Manufacturing of Bio-Based Greases,” NLGI Spokesman, 2014, 78(5), 24-35; and Wilkinson, M., et al., “Meeting the Challenges Posed by Environmentally Acceptable Lubricants,” NLGI Spokesman, 2015, 79(2), 6-9.
On the other hand, the ASTM D2670 method, even as found in its latest iteration, ASTM D2670-95 (Reapproved 2010), “Measuring Wear Properties of Fluid Lubricants (Falex Pin and Vee Block Method),” is limited to testing liquids such as, for example, mineral oils. Moreover, a rather large, 60-mL sample is required to be placed in the sample cup for immersion of the vee blocks during testing.
It would be desirable to improve upon the art of grease evaluation. It would be desirable, moreover, to ameliorate if not overcome drawbacks and shortcomings in the arts and fields such as set forth above. It would be desirable to provide the art of grease evaluation an alternative.